On May 19, 2015, the patient underwent a modified radical mastectomy, which consisted of whole breast mastectomy and axillary lymph node dissection. However, no lesions were found on the right breast during surgery. The IHC of the lymph node tissue was negative for estrogen receptor (Figure 4A), progesterone receptor (Figure 4B), prostate-specific antigen (PSA) (−), positive gross cystic disease fluid protein-15 (GCDFP-15), AE1/AE3, cytokeratin 7 (CK7), CK20, and human epidermal growth factor receptor 2 (HER2), while HER2 was amplified (negative) by FISH analysis (Figure 4C). Dissection of axillary demonstrated 0 of 17 signs of metastatic lymph nodes except for the original malignant axillary lymph node. Based on these findings, he was diagnosed with right axillary metastatic TNBC presumably from an OBC. According to American Joint Committee on Cancer Staging, the stage of cancer classification was II stage (T0N1M0). The patient was submitted to adjuvant chemotherapy with 4 cycles of TC (Paclitaxel: 270 mg, Cyclophosphamide: 0.9 g) and a rest of 21 days.


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(To view a larger version of Figure 4, click here.)

Following mastectomy, he experienced remarkable improvement of the dermal erythematous papules (Figure 5) and gradual recovery of muscle strength with normalization of creatinine kinase blood levels without glucocorticoid therapy.

Over >2 years of follow-up, the patient remained in good condition, without cutaneous or muscle DM recurrence or recurrence of breast cancer or other lesions.

DISCUSSION

OBC is defined by the presence of axillary metastases without an identifiable breast tumor. It accounts for 0.3%–1% of all newly diagnosed malignant diseases of the breast.1 A man’s lifetime risk of developing breast cancer is ~0.7%, but it has an increase in incidence in the seventh decade of life.2,3 Because of the rarity of OBC in men, the diagnosis and treatment can be challenging. Most of the studies available in the literature have demonstrated that there were several reasons for palpable axillary masses, most commonly being metastatic lymph nodes associated with breast cancer.4 When an axillary mass does occur, the most widely accepted method is to identify whether physical examination and imaging studies identify benign or malignant features. The next question is to confirm the primary source of disease.

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Data can also be obtained for immunocytochemistry through a core needle biopsy of the metastasis. In this case, immunohistochemical and FISH studies revealed ER (−), PR (−), HER2 (−), GCDFP-15 (+), AE1/AE3 (+), CK7 (+), CK20 (+), and PSA (−). Thus, we diagnosed the axillary tumor as primary breast cancer with axillary lymph node involvement. Based on immunohistochemical and FISH analyses of ER, PR, Ki-67, and HER2, a simplified classification was adopted to identify different subtypes of breast cancer. In the previous literature, it has been reported that most primary lesions of OBC exhibit a significantly higher positive rate for hormone receptors than that of female breast carcinomas.5 Our case was even more unusual being TNBC.